A high-performance liquid chromatography (HPLC) is usually used for separating and analyzing sparingly volatile or non-volatile components which are difficult to be analyzed by a gas chromatography (GC). The high-performance liquid chromatography has now been widely used for analyzing trace amounts of components in a variety of chemical fields, for analyzing the environment, for developing pharmaceuticals and for controlling qualities.
For the HPCL, there have heretofore been demanded to shorten the time for analysis, analyze the same of even a very small amount, and improve separation performance, as well as to decrease the size of the apparatus and to decrease the weight. To meet these demands, a number of proposals have heretofore been made concerning the liquid feed pump in the apparatus, decreasing the size of flow-path parts, decreasing the weight thereof, use of a separation column of a small diameter, improving the column efficiency and so on.
For example, JP-A-2003-107064 discloses an invention of a liquid feeding system for a high-performance liquid chromatograph which is compact, is of a low cost and is of the type of saving energy, JP-A-2005-257017 discloses an invention of a micro valve, and JP-A-2004-037266 discloses an invention for improving the efficiency of a separation column.
In recent years, in particular, liquid chromatographic apparatuses that feed the liquid in very small amounts have been vigorously studied by applying a high-speed and small-diameter separation column (micro column), and quite a few of them are utilizing a highly sophisticated and expensive system such as LC-MS/MS.
To attain the analysis at a higher speed and to improve the separation performance of the liquid chromatographic apparatus that feeds the liquid in very small amounts, however, it becomes necessary to increase the theoretic number of plates of the separation columns, to minimize the dead volume in the sample injection portion and in the flow path to minimize the diffusion of the sample components after the injection until arriving at the detection portion.
Therefore, efforts have been made to minimize the dead volume in the connection paths and in the valves. Concerning the micro columns, too, efforts have been made to improve the separation efficiency by further decreasing the diameter and by using a column packing of fine particles.